SENTENCE 1

There is a product on the market that is sold in a jar. The jar is inside a box.

There is a product on the market that is sold in a jar WHICH is inside a box.

WHICH here refers to 

SENTENCE 2

One kind of rubbish is thrown into dustbins while another is rubbish thrown anywhere else. This second kind is called litter.

One kind of rubbish is thrown into dustbins while another WHICH is thrown anywhere is called litter.

WHICH here refers to 

SENTENCE 3

Returnable bottles are often used forty or fifty times while non-returnable bottles are used only once. This is waste.

Returnable bottles are often used forty or fifty times while non-returnable bottles WHICH are used only once is waste.

WHICH here refers to 

SENTENCE 4

The British use 20 million paper bags every day. This may surprise you.

The British use 20 million paper bags every day WHICH may surprise you.

WHICH here refers to 

SENTENCE 5

Returnable bottles carry a deposit. This is repaid when the customer brings the bottle back.

Returnable bottles carry a deposit WHICH is repaid when the customer brings the bottle back.

WHICH here refers to